biology three

a really quick summary of the third module aqa biology gcse.

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  • Created by: kate
  • Created on: 20-05-10 13:42

exchange of gases

always: short distance to diffuse, rich blood supply, moist surface and large surface area!!

lungs:alveoli=large surface area, and thin walls on alveoli= short distance to diffuse, cappilaries surrounding alveoli=rich blood supply and always moist. exchange oxygen for carbon dioxide.

in small intestine: villi, folded=large surface area, covered in cappilaries=rich blood supply. digested food into blood, sometimes active transport.

active transport: uses energy from respiration, against the concentration gradient. (protein molecules in cell walls swiveling and collecting substances)

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Transporting substances around the body (circulati

two circulatory systems, heart to lungs(deoxgenated, lungs to haert oxygenated) and heart to body(oxygenated, body to heart deoxygenated).

heamoglobin in red blood cells reacts with oxygen to form oxyheamoglobin, this rection reverses when the blood reaches the body.

CO2, urea and digested food carried in blood plasma.

arteries, elastic, carry blood away from the heart, highpressure. Veins, low pressure, not elastic, carry blood to the heart.

when exercise: body need more oxygen and glucose for respiration to provide energy and waste substances ( CO2, lactic acid) to be removed quicker. so: blood vessels dialate, heart beats faster, breathe deeper and more quickly.

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gas exchange in plants

Water loss is an inveitable consequence of gas exchange.

minimise water loss: reduce surface area(spines), thick waxy cuticle, sunken stomata, stomata open at night(widened and narrowed by guard cells.

Water loss more on dry (air can hold more water), hot (more energy for evaporation), windy(water in the air blown away) days.

maximise gas exchange: increase surface area(flat leaves, root hairs), short distance to diffuse(thin leaves)

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transporting substances around the body (kidneys)

In the kidneys: small molecules diffuse from blood into tubuoles(glucose, water, urea, NOT protein), glucose is removed from the kidneys by active transport (see card 1), rest makes up urea.

Dialysis: treatment for kidney failure, blood passes through membrane in dialysis machine surrounded by 'perfect blood' this means the correct amount of each substance remains in the blood and the blood can be put back in the body. disadvantages, inconvenient(in hospital every few days for several hours), makes you ill when urea builds up between dialysis.

Transplant: get new kidney, has to match tissue type, person on immuno-suppressant drugs so has to be isolated.

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anerobic respiration

When not enough oxygen for aerobic respiration.

glucose goes to carbon dioxide+ lactic acid.

after exercise keep breathing deeply because need oxygen to break down the toxic lactic acid, this is oxygen debt.

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yeast: can tell apart from bacteria because DNA in nucleus and buds to reproduce.

making wine: crush grapes,yeast on skin of grapes anerobically respires on the natural sugars inside the grape, fermentation, produces ethanol.

making beer: from barley, when germinating enzymes break down the starch into sugar, add yeast, ferments sugar producing alcohol, hops added for flavouring.

making yogurt: add bacteria to milk, ferments lactose in milk into lactic acid which soldifys the milk into yogurt. to make into cheese add bacteria leave unil curds and whey, filter through muslin, leave longer and add bacteria for flavouring.

growing bacteria in school: at 25oC so harmful bacteria cannot grow hugely, sterilised innoculating loop, agar plate, wash and sterilise everything, lid sealed almost all the way round.

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industrial fermenters- stirrer(keep micro-organisms in suspension), water jacket(remove heat from respiration), air supply(if aerobic respiration), pH and tempreture monitors(so ensure proteins do not denature)

growing antibiotics: penicillin from bacteria Penicillium, grown in fermenters then nutrients removed, bacteria threatened so releases penicillin to kill competition= antbioltics.

Growing myco-proteins:fungus fusarium grown and then processes as an alternative to meat for vegatarians.

biogas:waste (excrement, compost), fermented, methane produced, used as fuel, on large and small scale.

biofuel: sugars (sugarcane, broken down maize), fermented ethanol produced, used as fuel. distilled before use.

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